Adds parameters to workspaces

Proposed changes

This PR allows to add parameters to workspaces. These parameters will be present in the contextManager (in the params object) as well as in the URL though query parameters (which allows to be able to reload / send the URL while maintaining the parameters).

They can also be specified in Wirecloud.changeActiveWorkspace through the options parameter, giving it a params attribute object.

Types of changes

What types of changes does your code introduce to the project: Put an x in the boxes that apply

[ ] Bugfix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

[x] I have read the CONTRIBUTING doc
[x] I have signed the CLA
[ ] I have added tests that prove my fix is effective or that my feature works
[ ] I have added necessary documentation (if appropriate)
[ ] Any dependent changes have been merged and published in downstream modules

Further comments

None

Wirecloud / wirecloud